1. Field of the Invention
This invention relates to a test device for nondestructive testing of tubular specimens. The test device uses a device and a process for detecting defects in these specimens by means of magnetic stray flux sensors.
2. Description of Related Art
Devices of the initially mentioned type are conventionally known. They consist of a host of test coils which are located annularly around the specimens and which are installed in a holding device. In this arrangement, the user has the choice of making either the diameter of the through opening through the arrangement of the test coils larger than the diameter of the specimens, or with a matched diameter of the arrangement of the test coils, accepting major wear on the arrangement of test coils. As the diameter of the arrangement of test coils becomes larger, the distance of the individual test coils from the surface of the specimen increases. Thus, the sensitivity of the measurement arrangement is reduced. Therefore, the layout of an arrangement of test coils of conventional design is always a compromise between measurement precision on the one hand and acceptable costs for replacement of the arrangement of test coils on the other. Replacement of the test coil arrangement becomes necessary when, for example, the specimens does not pass exactly centrally through the opening in the arrangement of test coils or raised faults on the surface of the specimens damage the arrangement of test coils.